The invention relates to a cutter for producing face gears, in particular a hob.
Face gears are gears which are used in angle drives with axes which may or may not intersect each other and may or may not form an angle of 90 degrees with each other. In this drive a cylindrical pinion meshes with a face gear whose teeth shape corresponds to the teeth shape of the cylindrical pinion.
The angle drive with face gear gearing has a number of special advantages compared with the generally known and used bevel gear drive, such as, inter alia, the absence of axial forces on the cylindrical pinion when it is designed with spur teeth, a greater transmission ratio being possible, the relatively simple adjustment, and a great transverse contact ratio which can be achieved without special facilities.
The absence of an economically feasible, and in addition accurate, manufacturing method was, however, hitherto one of the greatest problems for general use of the face gear gearing in highly loaded constructions. The absence of suitable manufacturing equipment played a major role in this.
The use of generating tools, by means of which face gears can be produced in a continuous process, is in practice a condition for the economic production of face gears and for a wider use of face gears in highly loaded and/or fast-running constructions.
A hobbing cutter for producing face gears is known from U.S. Pat. No. 2,304,586 (Miller). This cutter is a disc-shaped cutter body with cutting teeth provided on the periphery. The cutting edges of these cutting teeth are situated in a surface of revolution which is produced by turning an imaginary gear wheel of infinitely low thickness about the axis of the cutter body and simultaneously about its own axis, during which the imaginary gear wheel on one revolution about the axis of the cutter body turns about its own axis through an angle which is equal to a whole number of times the pitch angle of the imaginary gear wheel, and the plane of the imaginary gear wheel always extends in the radial direction of the cutter body and at right angles to the path described by the teeth of the imaginary gear wheel.
The cutting teeth are provided with clearance faces in the same way as ordinary cutting teeth of a cutter.
The known cutter has, however, the disadvantage that during the re-grinding of the cutting teeth the shape of the cutting edge of the cutting teeth changes, so that the shape of the face gear teeth formed with the re-ground cutter will also change. This is undesirable.